misc/eeprom: add driver for microwire 93xx46 EEPROMs

Add EEPROM driver for 93xx46 chips.  It can also be used with spi_gpio
driver to access 93xx46 EEPROMs connected over GPIO lines.  This driver
supports read/write/erase access to the EEPROM chips over sysfs files.

[rdunlap@xenotime.net: fix printk format]
Signed-off-by: Anatolij Gustschin <agust@denx.de>
Cc: Jonathan Cameron <jic23@cam.ac.uk>
Cc: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>